In general, inkjet printing machines, also known as imaging devices or printers, include at least one printhead that ejects drops of liquid ink either directly onto recording media or onto an ink image receiving surface for transfer to recording media. A phase change inkjet printer employs phase change inks that are in the solid phase at ambient temperature, but they transition to a liquid at an elevated temperature. The melted ink is then ejected as ink drops by a printhead to form an ink image.
One type of inkjet printer is a continuous web printer. In this type of printer, a media web is unwound from a supply roller and directed through a feed path that passes by one or more printheads for formation of an ink image directly onto the sheet. The continuous web is pulled through the printer by driven rollers. Tension is maintained on the web to enable movement of the web by moveable tension bars or rollers, which remove slack from the web so the web remains taut without breaking.
Regardless of the type of media, proper image durability and quality is achieved by heating the media both prior to printing and fixing the ink image onto the web. In web-fed printers, media heaters typically comprise one or more radiant heaters positioned along the media pathway for exposing the media to a sufficient amount of thermal energy to regulate the temperature of the moving web. Thermal output of the radiant heaters is controlled by adjusting the power supplied to the heaters. The printing system typically includes a thermal sensor positioned adjacent the media pathway to detect the temperature of the moving web and provide the detected temperatures to a controller. The controller can then adjust the electrical power provided to the heaters with reference to the detected temperatures of the web to adjust the temperature of the media web.
A schematic diagram for a typical continuous web printer that includes multiple printheads that eject melted phase change ink on the moving web to form an ink image on the web is illustrated in FIG. 5. The solid ink printer, hereafter simply referred to as a printer 110, implements a solid ink print process for printing onto a continuous media web. To this end, the printer 110 includes a web supply and handling system 160, a phase change ink printing system 114, and a web heating system 120.
The web supply and handling system 160 can include one or more media supply rolls 138 for supplying a media web 112 to the printer 110. The supply and handling system 160 is configured to feed the media web 112 in a process direction 130 in a known manner along a media pathway in the printer 110 through the print zone 118, and past the web heating system 120 and fixing assembly 150. To this end, the supply and handling system 160 can include any suitable arrangement of components 164, such as rollers, idler rollers, tensioning bars, etc., for moving the media web 112 through the printer 110. The web supply and handling system 160 can include a take-up roller 139 for receiving the media web 112 after printing operations have been performed.
The phase change ink printing system 114 includes a plurality of printhead assemblies, which are appropriately supported to enable one or more printheads within these assemblies to eject drops of ink directly onto the media web 112 as the web moves through the print zone 118. The printing system 114 can be incorporated into either a carriage type printer, a partial width array type printer, or a page-width type printer.
Ink is supplied to the printhead assemblies within the printing system 114 from a solid ink supply (not shown). Since the phase change ink printer 110 is a multicolor device, the ink supply includes multiple sources of different colors of phase change solid ink. The phase change ink system also includes a solid phase change ink melting assembly (not shown) for at least each color of ink to melt and deliver liquid ink to one of the printhead assemblies in the printing system 114. The liquid ink is supplied to one or more printheads in a printhead assembly by gravity, pump action, or both.
Once the drops of ink have been ejected by the printing system 114 onto the moving media web 112 to form an ink image, the media web 112 is moved through a fixing assembly 150 which spreads the ink enabling proper image durability and quality. In the embodiment of FIG. 5, the fixing assembly 150 comprises at least one pair of fixing rollers 154 that are positioned in relation to each other to form a nip through which the media web 112 is fed. The ink drops on the media web 112 are pressed into the web 112 and spread on the web 112 by the pressure formed by the nip. Although the fixing assembly 150 is depicted as a pair of fixing rollers, the fixing assembly 150 can be any suitable type of device or apparatus, as is known in the art, which is capable of fixing the image to the media web 112.
Operation and control of the various subsystems, components, and functions of the printer 110 are performed with the aid of a controller (not shown in FIG. 5). The controller can be implemented as hardware, software, firmware, or any combination thereof. In one embodiment, the controller comprises a self-contained, microcomputer having a central processor unit and electronic storage as is known in the art. The controller is configured to coordinate the operation of the systems within the printer to produce printed ink images on media that correspond to image data received from one or more image data sources.
In the embodiment of FIG. 5, the web heating system 120 includes heaters integrated into a preheating drum 124 and a leveler roller 126. Additionally, radiant heaters 128 are also positioned along the feed path for regulation of the web temperature. Such heated rollers and radiant heaters are known in the art. The preheating drum 124 is positioned upstream from the printing system 114 to heat the portion of the media web 112 opposite the drum 124 prior to that portion of the web reaching the print zone 118. This media heating facilitates the ink adhesion to the web 112 as well as secondary color mixing. The leveler roller 126 is positioned downstream from the printing system 114 to heat the media web 112 after ink has been applied to the media web 112 to help the different layers of ink on the media web 112 reach a uniform temperature. The radiant heaters 128 are positioned downstream from the printing system 114 and the leveler roller 126 in order to heat the media web 112 to a temperature appropriate for fixing the ink image to the web 112 at the fixing assembly 150.
The web heating system 120 can be configured to heat the media web 112 to any suitable temperature dependent upon a number of factors including web speed, web type, ink type, position along the media pathway, etc. For example, the web heating system 120 can be configured to heat the media web 112 to approximately 55 degrees Celsius at the preheating drum 124 prior to printing to the web. The web heating system 120 can also be configured to heat the media web 112 to approximately 30 degrees Celsius at the leveler roller 126.
Ink sometimes escapes from the printhead assemblies in the printing system 114 and migrates to the surface of the preheating drum 124 or the leveler roller 126. Even the intermittent release of melted ink onto one or both of these rollers can accumulate to a level capable of producing defects on prints by interfering with the movement of the media web 112 about the preheating drum 124 and/or the leveler roller 126. Manually cleaning accumulated ink from the preheating drum 124 or leveler roller 126 is a time consuming and labor intensive process because features within the printer 110 are difficult to access without dismantling at least part of the printer 110. Additionally, the printer 110 cannot be used to generate printed images when the drum 124 or the leveler 126 is manually cleaned. Accordingly, a process for cleaning ink off the preheating drum 124 and/or the leveler roller 126 that minimally interferes with use of the printer is desirable.